Aircraft: FIGHTER
Phase of flight: Final Approach
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy

During a yearly military exercise the LOA (Letter of Agreement) between TRACON and ARTCC dictates that the separation between a flight of 2 or less fighters must be 10 miles. A flight of more than 2 fighters must have a minimum of 15 miles spacing. Altitude separation is not used as a means of separation since they are cleared on the approach by center and the aircraft will be descending via the arrival. All fighter flights were non-standard during this recovery. Moderate to extreme precipitation was reported 20 miles north of their destination airport. No bases reported; but the tops were reported at 18000 ft. This precipitation was depicted on my radar and appeared to be moving south along the arrival path.During the recovery of flights during this operation the airport of intended landing was reporting IMC; so the fighters were doing an IFR recovery via the STAR to an ILS Approach. ZAN handed off to me a flight of 4 fighters (Flight X); and a second (Flight Y) with 7 miles in trail spacing; less than 1;000 ft; and both flights cleared on the arrival. Flight X was cleared on the ILS Approach; the Flight Y was then cleared on the approach with 5 miles spacing and decreasing. When Flight Y was on a 7 mile final with less than 4 miles spacing; I cancelled the approach clearance and gave them an altitude to maintain and upon reaching an altitude a heading for re-sequence. Center was still sending fighter flights inbound on the approach; but stopping the flights at 11;000 ft. I was still only getting 6-10 mile in trail spacing for flights of 2-4 with nothing but altitude separation through the moderate to extreme precipitation. Center handed off to me an emergency aircraft descending; direct to the IAF not cleared on the approach. The lead aircraft (the one who was initially coordinated as an emergency) did not have a data block. I had to get the aircraft to ident to properly radar contact the flight as well as manually input the data for the data block to acquire. After some questioning; the pilot was minimum fuel and closing on BINGO fuel.Flight Z of 4 fighters came onto my frequency without a handoff or a data tag; IFR; direct to a fix. I had to again get the pilot to ident to properly radar identify the target; then manually input the data and scratchpad to indicate information about how many and what the flight was cleared on; as per our LOA. I sequenced Flight Z behind the emergency flight of 4 aircraft; then the Flight Y flight in trail. My Supervisor was doing all of my coordination during this time. Center advised us that the fighters were all approaching BINGO fuel. They coordinated to send the remaining fighters to hold over a fix and stack the fighter flights. Center did not have the data blocks input; the rest of the fighters were IFR; and switched to my frequency all during the time of the emergency flight and onward. While during the sequencing of inbounds and re-sequencing of the Flight Y flight; the rest of the fighters were calling me for clearances. I was also properly attempting to radar identify each flight as well as manually type in the data information for each separate flight; while also clearing aircraft on the approach. In order to provide in trail spacing on final for the aircraft inbound from Center; as well as the re-sequenced Flight Z. I had to take multiple flights off of the arrival and send them on a west bound heading descending to an altitude not to conflict with the other flights. I cleared Flight Y flight on the ILS approach. I saw that the speed and spacing was good and switched the aircraft as per the LOA prior to the aircraft reaching a 7 mile final. I refocused my attention back to the aircraft coming inbound as well as the fighters stacked over the initial approach fix for the ILS Approach. My Supervisor brought to my attention the spacing between the trail aircraft of Flight Z and the lead flight of Flight Y. When I measured out the spacing between the aircraft; it was less than 3 miles and appeared to be less than 1;000 ft separation. The indicated speed of the trail aircraft was 180 kts over the ground; while the indicated speed of Flight Y was 350 plus knots over the ground at a 4-5 mile final inside of their destination Class D airspace.Recommend to follow the established procedures outlined in the LOA's. I recommend to stop coordinating different things; on the fly the week of the operation; that is not outlined in the LOA. It not only adds complexity but also confuses the controllers involved of what we are and are not doing. Some Approach Controllers are having to coordinate with the current Center controller with different things to figure out what exactly is going on and who is doing what. It also adds complexity to the pilots involved in flying it because they don't know which one to apply or get confused of the instruction issued by approach; especially the foreign pilots in this exercise. This has been happening for the past 2 exercises. The LOA between TRACON and Center is over a year old and contains items that we do not do anymore; is done differently; or is coordinated the week of to do the complete opposite of what the Military Exercise LOA prescribes. A TRACON Controller reported that the Center was handing off aircraft recovering from a military exercise with less than the prescribed spacing specified in the Letter of Agreement.